Semiconductor integrated circuits are often formed by subjecting a semiconductor substrate to a series of processing steps by which an array of integrated circuits are formed on the substrate. The substrate is commonly, for example, a wafer formed of a crystalline semiconductor material. A common choice for the semiconductor material is silicon. The wafer is ultimately separated by dicing the wafer into various sections (each section being commonly referred to as a “die”) in a manner that each die includes a corresponding integrated circuit. Each die is then packaged.
Once the integrated circuits are formed on the wafer, and prior to dicing the wafer, each integrated circuit on the wafer may be tested to verify proper operation. Typically, such testing might be attempted under the anticipated environmental operating extremes under which the integrated circuit is expected to operate. For examples, circuits may be anticipated to operate under different temperature, pressure, voltage, acceleration, noise or under other environmental conditions.
During testing of a particular wafer, the wafer is transported to a wafer test machine, wherein the various integrated circuits of the wafer may be tested. To test each integrated circuit, the wafer test probe head includes various probes that make mechanical and electrical contact with the various contacts of the integrated circuit under test. The integrated circuit is then tested by having the probe head apply test signals and power supplies to the integrated circuit through the probes, and by measuring appropriate response signals received back from the integrated circuit under test. Based on the response signals received, the wafer test machine may verify whether or not the integrated circuit is operating properly. The testing machine may then record which integrated circuits on the wafer passed the electrical test, and which failed the electrical test. The test results may be used later in the process when the wafer is diced into its various die. If the particular wafer is to be tested under anticipated environmental operating extremes, the probe head is also typically subjected to the same testing conditions. Likewise, any support circuitry contained on the test board which interfaces with the circuit under test is also typically subjected to the same testing conditions.